1. Field of the Invention
The present invention relates to a fuel cell system and a method for recovering performance of a fuel cell.
2. Description of the Related Art
If a fuel cell is operated for a long time, various impurities will be adsorbed on an electrode of the fuel cell and power generation performance thereof will be reduced. According to a known method for recovering the performance of the electrode on which the impurities are adsorbed, a potential of the electrode is increased so that the impurities, such as sulfur, adsorbed on the electrode are oxidized and are thereby removed. See, for example, Japanese Unexamined Patent Application Publication No. 2008-077884.
According to the above-described method, the fuel cell is maintained in a high-potential state so as to oxidize sulfur species adsorbed on a catalyst surface. However, if the fuel cell is maintained in a state in which the electrode potential is at a no-load potential or a high potential close to the no-load potential, there is a risk that an electrolyte membrane of the fuel cell will be degraded or elution of the catalyst metal will occur.